Anticipating
a succulent meal, we begin to salivate. This complex mixture of over 200
proteins helps us digest our food. But Menno Oudhoff, a graduate student at the
Amsterdam Academic Center for Dentistry, found another purpose for saliva in
looking at the oral epithelial cells that line the mouth. It closes wounds.

It is
known that rodents lick each other's wounds and that may speed up the healing
process. But rat saliva, which contains high levels of growth hormones, is very
different from what we produce. So Oudhoff collected saliva from healthy
members of his lab.

Oral
epithelial cells were grown in a thin layer on a dish. Some were scratched away
to simulate a wound. Oudhoff then added saliva and the "wound" closed
up.

But
not all saliva works the same. Some
people's saliva closed wounds more effectively than others. Oudhoff says not
only is there a huge variation in saliva between people, but "also during
the day, you have a different secretion rate -- when you sleep you hardly have
any saliva."

Oudhoff
determined that the active compound in human saliva wound closure is histatin,
a known antifungal. This is present in humans and a couple of primate species,
but not rodents.

Since
our mouths are filled with bacteria, some pathogenic, Oudhoff says that
wound-closing compounds like histatins may protect us from getting infections
when we get a cut in our mouth. Still, without further study Oudhoff does not
suggest people start licking their wounds.

This
work was published online this month by The Journal of the Federation of
American Societies for Experimental Biology.